What you need to do before you start

Replacing a bike tube means removing the old, punctured tube and installing a new one inside the tire. You'll need a new tube that matches your wheel size (printed on the tire sidewall, like 26" or 700c), two tire levers to pry the tire off the rim, and a pump to inflate the new tube. If you don't know your wheel size, bring the old tube or tire to a bike shop and they'll tell you in seconds.

Work on a flat surface where you can see what you're doing. Flip the bike upside down so the wheel you're fixing points up, or use a bike stand if you have one. Remove the wheel from the frame first—for the front wheel, open the quick-release lever or unscrew the axle nuts; for the rear wheel, shift to the smallest gear, open the quick-release, and pull the derailleur back to clear the chain.

Once the wheel is off, let out any remaining air in the old tube by pressing the valve. This makes the next step easier.

Key Takeaways

  • You need a new tube that matches your wheel size, two tire levers, and a pump before you start.
  • Remove the wheel from the frame, then use tire levers to pry one edge of the tire off the rim and pull out the old tube.
  • Before installing the new tube, check inside the tire for thorns, glass, or sharp objects that caused the puncture.
  • Inflate the new tube slightly before seating it in the tire, then work the tire bead back onto the rim by hand and with levers.
  • Inflate fully and check that the tire bead sits evenly on both sides of the rim before reinstalling the wheel.

Remove the tire from the rim using tire levers

Insert a tire lever under the tire bead (the edge of the tire) about 6 inches away from the valve. Pry the bead up and over the rim edge. Slide the lever around the rim to lift one full side of the tire off—you don't need to remove the whole tire, just one bead.

Once one side is free, reach in and pull out the old tube. Start at the valve and work your way around, being careful not to pinch the tire with your fingers. The tube should come out easily once one bead is lifted.

Inspect the tire for what caused the puncture

Before you install the new tube, run your fingers slowly along the inside of the tire, feeling for thorns, glass shards, or sharp metal. This is the most important step—if you don't remove what punctured the first tube, the new one will fail in the same spot.

Look at the outside of the tire too. If you see a thorn sticking through, mark that spot on the inside and check it carefully. If the tire has a large gash or the sidewall is torn, the tube will bulge out and fail; in that case, the tire itself needs replacing, not just the tube.

Install the new tube and reseat the tire

Inflate the new tube just enough so it holds its shape—about 20% of final pressure. This prevents it from twisting or pinching as you work. Fit the valve through the rim hole first, then tuck the tube evenly inside the tire all the way around.

Starting opposite the valve, use your hands to roll the tire bead back onto the rim. Work your way around in both directions, pushing the bead down and inward. When you're close to finishing, the last section will be tight—this is normal. If you can't get it by hand, use a tire lever, but be very careful not to pinch the new tube. Insert the lever under the bead only, not under the tube.

Inflate and check the seal

Once the tire bead is fully seated on the rim, inflate the tube to the pressure marked on the tire sidewall (usually between 40 and 100 psi depending on the tire type). As you pump, watch both sides of the rim to make sure the tire bead rises evenly and stays seated. If one side bulges out more than the other, stop, let out some air, and reseat that section by hand.

When the tire is fully inflated, spin the wheel and look at the gap between the tire and rim on both sides. The gap should be even all the way around. If it's uneven, the bead isn't seated correctly and the tube will fail. Let out air, adjust, and try again.

Reinstall the wheel on the frame

Once the tire is seated and inflated, reinstall the wheel. For the front wheel, align it in the fork and tighten the quick-release or axle nuts. For the rear wheel, pull the derailleur back, fit the chain onto the smallest cog, and slide the wheel into the dropouts, then tighten.

Spin the wheel to make sure it doesn't rub on the brake pads or frame. If it does, the wheel isn't centered—remove it and try again. Once it spins freely, you're done.

When to call a bike shop instead

If the tire won't seat no matter how many times you try, the rim may be bent or the tire bead may be damaged. If you find a large gash in the tire or the sidewall is torn, the tire needs replacing. If the valve is damaged or leaking, you need a new tube with a working valve. Any of these situations is worth a trip to a bike shop rather than repeated attempts at home.

Shops can also identify what caused the puncture if you're not sure—sometimes a slow leak comes from a pinhole you can't see, and sometimes the problem is the rim tape, not the tube. A mechanic can spot these in seconds.

Frequently Asked Questions

How do I know what size tube to buy?

Look at the sidewall of your tire—it will say something like "26 x 2.0" or "700 x 28c". That first number is your wheel size. Bring the old tube or a photo of the tire to a bike shop if you're unsure, and they'll hand you the right one in seconds.

Can I patch the old tube instead of replacing it?

You can, but only if the hole is small and you have a patch kit. Patches work best for slow leaks and tiny punctures. If the hole is large, the valve is damaged, or you've already patched it once, a new tube is more reliable and costs $8 to $15.

What if I pinch the new tube while reinstalling the tire?

You'll hear a hiss or see the tube bulge out. Stop when ready, let out the air, and remove the tire bead again. Inspect the tube for the pinch hole—if it's small, you can patch it. If it's large or the valve is damaged, install another new tube and be more careful with the levers the second time.

How tight should I inflate the new tube?

Inflate to the pressure printed on the tire sidewall. This is usually between 40 and 100 psi depending on tire width and type. Check the sidewall, not the rim, and use a pump with a pressure gauge so you don't over- or under-inflate.

Why does my new tube keep going flat?

The most common reason is a sharp object still inside the tire—thorns, glass, or metal fragments. Before installing the next tube, run your fingers very slowly around the inside of the tire and look for anything sticking through. The second most common reason is the tire bead not being fully seated, which causes the tube to pinch. Make sure the bead sits evenly on both sides of the rim before you finish inflating.